Tubular metal products in the form of pipe, etc., have been produced in the past by a variety of techniques including casting which have been described in detail in the published literature relating to this art. U.S. Pat. No. 4,274,470-issued June 23, 1981 in the prior art statement thereof appearing in columns 1 and 2, for example, lists a number of prior art patents and technical articles which describe electromagnetic casting apparatus suitable for use in the fabrication of tubular metal products, such as pipe, and discusses the short-comings of these known prior art procedures. Included amongst these prior art disclosures are U.S. Pat. No. 3,467,166--Getselev, et al.; U.S. Pat. No. 3,605,865--Getselev; U.S. Pat. No. 3,735,799--Karlson; U.S. Pat. No. 4,014,379--Getselev; and U.S. Pat. No. 4,126,175--Getselev which describe the use of an electromagnetic mold to contain a pool of molten metal within specified dimensions while the pool is moving downwardly and in which outer, laterally extending portions of the pool are being solidified. In this procedure, accretion of the solidified metal is longitudinally extending and melt being delivered, either semi-continuously or continuously, is by gravity flow to the upper end of the descending pool that forms the solidifying ingot. One of the more serious drawbacks of this procedure is the fact that the "fail safe" characteristics of previously known upward casting technique, is absent. Hence, in the event of an unexpected electric power failure, etc., molten metal may spill out of the downwardly moving pool of molten metal instead of merely running back into a holding vessel as would be the case in an upward casting system. In addition, the molten metal overflow and break-out possibility in these known downward casting techniques require constant careful control of both the molten metal feed rate and the solidified ingot removal rate with both rates being drastically limited by a heat exchange problem which consequently diminishes the commercial potential for this method of continuous casting.
U.S. Pat. No. 3,746,077 to Lohikoski, et al. and U.S. Pat. No. 3,872,913 to Lohikoski, both assigned to Oytokumpo Oy of Finland, describe an upward casting technique wherein molten metal either is hydrostatically forced or pulled by vacuum upwardly into an open-ended, vertically disposed mechanical mold as freshly-formed. By this procedure cooled cast product intermittently is removed from physical contact with the upper end of the mechanical mold into which the molten metal continuously is being introduced. In this system, the desirable "fail-safe" characteristic of an upward-casting technique is attained but only at the expense of considerable wear and tear on an external contact mold which wears out in unacceptably short time periods during continuous or semi-continuous operation of the system. Thus, there is a need for an improved system of continuous casting of tubular metal product which avoids the shortcomings of the known prior art electromagnetic casting systems.